Cold potatoes could counter health effects of red meat

Next time you fire up the barbecue, don’t forget the potato salad. It could help counter the effects of all that red meat.

People who eat a lot of red meat have a higher risk of developing colorectal cancer. But previous work has suggested that a type of starch that doesn’t get digested – called resistant starch – can have a protective effect by raising levels of a chemical that dampens some of the genetic changes that precede such cancers.

In the first, small human trial, Karen Humphreys and her colleagues from Flinders University, Adelaide, Australia, gave 23 healthy volunteers a high red-meat diet for four weeks. They then took cell samples from the volunteers’ guts. These showed an increase in the number of micro RNA molecules – short lengths of genetic material that can silence genes – called miR17-92 and miR21. These elevated micro RNAs are associated with the survival and growth of colorectal cancer cells, and with poorer outcomes for people with that type of cancer.

Advertisement

Next they gave the same volunteers the same diet for another month , but this time supplemented with resistant starch. This is found in foods including cooked potato that has been left to cool, and bananas, though the researchers gave it in the form of a drink.

After this time, cell samples showed that the volunteers’ levels of miR17-92 had, on average, reverted to their original level before the high red-meat diet was introduced. The starch-supplemented diet had no impact on the levels of miR21.

The changes are indicative of much more going on, says Humphreys. “Red meat is likely to be having other cellular effects aside from changing micro RNA levels, such as damage to DNA,” she says, adding that she and her team are now looking at whether resistant starch also moderates other effects.

“Red meat should be eaten in small amounts only and foods that contain fibre or resistant starches should be an important part of the diet,” says John Cummings, a gastroenterologist at Dundee University, UK.